linux-kernel - Re: [PATCH RFC 2/3] x86/kvm/hyper-v: move VMX controls sanitization out of nested_enable

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <f15d9e98-25e9-2031-2db5-6aaa6c78c0eb@redhat.com>
Date:   Wed, 22 Jan 2020 17:40:27 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Vitaly Kuznetsov <vkuznets@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     kvm@...r.kernel.org, Jim Mattson <jmattson@...gle.com>,
        linux-kernel@...r.kernel.org, Liran Alon <liran.alon@...cle.com>,
        Roman Kagan <rkagan@...tuozzo.com>
Subject: Re: [PATCH RFC 2/3] x86/kvm/hyper-v: move VMX controls sanitization
 out of nested_enable_evmcs()

On 22/01/20 17:29, Vitaly Kuznetsov wrote:
> Yes, in case we're back to the idea to filter things out in QEMU we can
> do this. What I don't like is that every other userspace which decides
> to enable eVMCS will have to perform the exact same surgery as in case
> it sets allow_unsupported_controls=0 it'll have to know (hardcode) the
> filtering (or KVM_SET_MSRS will fail) and in case it opts for
> allow_unsupported_controls=1 Windows guests just won't boot without the
> filtering.
> 
> It seems to be 1:1, eVMCSv1 requires the filter.

Yes, that's the point.  It *is* a hack in KVM, but it is generally
preferrable to have an easier API for userspace, if there's only one way
to do it.

Though we could be a bit more "surgical" and only remove
SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES---thus minimizing the impact on
non-eVMCS guests.  Vitaly, can you prepare a v2 that does that and adds
a huge "hack alert" comment that explains the discussion?

Paolo